Magnetic structures, semiconductor structures, and semiconductor devices

ABSTRACT

Memory cells are disclosed. Magnetic regions within the memory cells include an alternating structure of magnetic sub-regions and coupler sub-regions. The coupler material of the coupler sub-regions antiferromagnetically couples neighboring magnetic sub-regions and effects or encourages a vertical magnetic orientation exhibited by the neighboring magnetic sub-regions. Neighboring magnetic sub-regions, spaced from one another by a coupler sub-region, exhibit oppositely directed magnetic orientations. The magnetic and coupler sub-regions may each be of a thickness tailored to form the magnetic region in a compact structure. Interference between magnetic dipole fields emitted from the magnetic region on switching of a free region in the memory cell may be reduced or eliminated. Also disclosed are semiconductor device structures, spin torque transfer magnetic random-access memory (STT-MRAM) systems, and methods of fabrication.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/112,125, filed Aug. 24, 2018, pending, which is a continuation ofU.S. patent application Ser. No. 15/642,577, filed Jul. 6, 2017, nowU.S. Pat. No. 10,121,824, issued Nov. 6, 2018, which is a continuationof U.S. patent application Ser. No. 15/168,054, filed May 29, 2016, nowU.S. Pat. No. 9,711,565, issued Jul. 18, 2017, which is a continuationof U.S. patent application Ser. No. 14/728,268, filed Jun. 2, 2015, nowU.S. Pat. No. 9,356,229, issued May 31, 2016, which is a continuation ofU.S. patent application Ser. No. 13/527,262, filed Jun. 19, 2012, nowU.S. Pat. No. 9,054,030, issued Jun. 9, 2015, the disclosure of each ofwhich is hereby incorporated in its entirety herein by this reference.

TECHNICAL FIELD

The present disclosure, in various embodiments, relates generally to thefield of memory device design and fabrication. More particularly, thepresent disclosure relates to design and fabrication of memory cellscharacterized as spin torque transfer magnetic random-access memory(STT-MRAM) cells.

BACKGROUND

Magnetic Random-Access Memory (MRAM) is a non-volatile computer memorytechnology based on magnetoresistance. One type of MRAM cell is a spintorque transfer MRAM (STT-MRAM) cell, such as that illustrated inFIG. 1. A conventional STT-MRAM cell includes a magnetic cell core 100supported by a substrate 102. The magnetic cell core 100 includes atleast two magnetic regions, for example, a “fixed region” 130 and a“free region 170,” with a non-magnetic region 160 in between. One ormore lower intermediary regions 120 and one or more upper intermediaryregions 180 may be disposed under and over, respectively, the magneticregions (e.g., the fixed region 130 and the free region 170) of themagnetic cell core 100 structure.

An STT-MRAM cell configured to exhibit perpendicular magnetic anisotropy(“PMA”) includes the fixed region 130 that has a fixed, verticalmagnetic orientation and includes the free region 170 that has avertical magnetic orientation that may be switched, during operation ofthe cell, between a “parallel” configuration (FIG. 1) and an“anti-parallel” configuration (FIG. 2). In the parallel configuration(FIG. 1), a magnetic orientation 171 of the free region 170 is directedessentially in the same direction (e.g., north or south) as a magneticorientation 131 of the fixed region 130, giving a lower electricalresistance across the magnetoresistive elements, i.e., the fixed region130 and free region 170. This state of relatively low electricalresistance may be defined as a “0” state of the MRAM cell. In theanti-parallel configuration (FIG. 2), a magnetic orientation 172 of thefree region 170 is directed essentially in the opposite direction (e.g.,north or south) of the magnetic orientation 131 of the fixed region 130,giving a higher electrical resistance across the magnetoresistiveelements, i.e., the fixed region 130 and free region 170. This state ofrelatively high electrical resistance may be defined as a “1” state ofthe MRAM cell.

Switching of the magnetic orientation 171, 172 of the free region 170and the resulting high or low resistance states across themagnetoresistive elements enables the write and read operations of thetypical MRAM cell. In operation, a programming current may be caused toflow through an access transistor and the magnetic cell core 100. Thefixed region 130 within the magnetic cell core 100 polarizes theelectron spin of the programming current, and torque is created as thespin-polarized current passes through the magnetic cell core 100. Thespin-polarized electron current interacts with the free region 170 byexerting a torque on the free region 170. When the torque of thespin-polarized electron current passing through the magnetic cell core100 is greater than a critical switching current density (J_(c)) of thefree region 130, the torque exerted by the spin-polarized electroncurrent is sufficient to switch the direction of the magnetization,i.e., between magnetic orientation 171 and magnetic orientation 172, ofthe free region 170. Thus, the programming current can be used to causethe magnetic orientation 171, 172 of the free region 170 to be alignedeither parallel to (FIG. 1) or anti-parallel to (FIG. 2) the magneticorientation 131 of the fixed region 130.

Ideally, the amount of programming current required to switch the freeregion 170 from the parallel configuration (FIG. 1) to the anti-parallelconfiguration (FIG. 2) is essentially the same amount of programmingcurrent required to switch from the anti-parallel configuration (FIG. 2)to the parallel configuration (FIG. 1). Such equal programming currentfor switching is referred to herein as “symmetric switching.”

Though symmetric switching may be ideal, in conventional magnetic cellcores 100, one or more magnetic regions, because of their magneticnatures, may emit a magnetic dipole field, which may interfere withswitching in the free region 170. For example, a magnetic dipole field132 may be emitted by the fixed region 130, as illustrated in FIGS. 1and 2. (Notably, though the magnetic dipole field 132 is illustrated aspassing between essentially the entirety of an upper surface and a lowersurface of the fixed region 130, in actuality, the fixed region 130 mayhave a height substantially smaller than the width of the fixed region130, such that the magnetic dipole field 132 may be emitted from upperand lower surfaces essentially proximate only to sidewalls of the fixedregion 130.) When the free region 170 is in one configuration, e.g., theparallel configuration (FIG. 1), the magnetic orientation 171 of thefree region 170 may be in at least partial parallel alignment with themagnetic dipole field 132 from the fixed region 130; however, when thefree region 170 is in the other configuration, e.g., the anti-parallelconfiguration (FIG. 2), the magnetic orientation 172 of the free region170 may be in at least partial anti-parallel alignment with the magneticdipole field 132. As illustrated in FIGS. 1 and 2, then, the magneticdipole field 132 may be emitted from an upper surface of the fixedregion 130 and pass through a portion of the free region 170 beforearcing to enter a lower surface of the fixed region 130. When the freeregion 170 is in the parallel configuration (FIG. 1), both the magneticdipole field 132 from the fixed region 130 and the magnetic orientation171 of the free region 170 may be directed in essentially the samedirection (e.g., upwards and upwards, respectively). However, when thefree region 170 is in the anti-parallel configuration (FIG. 2), themagnetic dipole field 132 from the fixed region 130 and the magneticorientation 172 of the free region 170 may be directed in essentiallyopposite directions (e.g., upwards and downwards, respectively). Hence,the free region 170 may have a higher affinity for being in the parallelconfiguration (FIG. 1) than in the anti-parallel configuration (FIG. 2)such that more programming current may be needed to switch the freeregion 170 to the anti-parallel configuration (FIG. 2) from the parallelconfiguration (FIG. 1) than is needed to switch the free region 170 fromthe anti-parallel configuration (FIG. 2) to the parallel configuration(FIG. 1). The presence of the magnetic dipole field 132 emitted from thefixed region 130 may, therefore, impair the ability to symmetricallyswitch the magnetic orientation 171, 172, of the free region 170 duringoperation of the MRAM cell.

Efforts have been made to eliminate the negative effects on switchingdue to interference from a stray magnetic dipole field 132. Theseefforts include, for example, attempts to neutralize the magnetic dipolefield 132 by balancing magnetic orientations within the magnetic region,e.g., the fixed region 130. For example, FIG. 3 illustrates aconventional fixed region 330 including magnetic material 334 separatedby conductive material 336. A coupler material 338 couples a lowerregion and an upper region of the fixed region 330. The conductivematerial 336, disposed between the magnetic material 334, causes themagnetic material 334 to exhibit a perpendicular anisotropy, i.e.,vertical magnetic orientations 331, 333, while the coupler material 338is formulated and positioned to provide anti-parallel coupling ofadjacent magnetic material. Thus, the fixed region 330 is configured asa synthetic antiferromagnet (SAF) with the upper region and the lowerregion of the fixed region 330 coupled via a single intervening couplermaterial 338. The goal is that a magnetic dipole field emitted by theupper region will be effectively cancelled by a magnetic dipole fieldemitted by the lower region due to the opposite directions of themagnetic orientations 331, 333. However, the free region of the cellwill be disposed closer to one of the upper and lower regions of thefixed region 330 such that the free region will experience the magneticdipole field emitted by the more proximal of the upper and lower regionsmore strongly than the free region will experience the other magneticdipole field. Thus, balancing the magnetic orientations of the upper andlower regions may not effectively cancel a magnetic dipole fieldexperienced by the free region of the cell. Hence, designing a cell corestructure that achieves symmetrical switching of the free region hasbeen a challenge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional, elevation, schematic illustration of amagnetic cell core of a conventional STT-MRAM cell including a freeregion in a parallel configuration.

FIG. 2 is a cross-sectional, elevation, schematic illustration of themagnetic cell core of the conventional STT-MRAM cell of FIG. 1 includingthe free region in an anti-parallel configuration.

FIG. 3 is a cross-sectional, elevation, schematic illustration of afixed region of a conventional STT-MRAM cell.

FIG. 4 is a schematic diagram of an STT-MRAM system having a memory cellaccording to an embodiment of the present disclosure.

FIG. 5 is a cross-sectional, elevation, schematic illustration of afixed region of an STT-MRAM cell according to an embodiment of thepresent disclosure.

FIG. 6 is a cross-sectional, elevation, schematic illustration of a cellcore structure of an STT-MRAM cell according to an embodiment of thepresent disclosure, the STT-MRAM cell including the fixed region of FIG.5.

FIG. 7 is a cross-sectional, elevation, schematic illustration of a cellcore structure of an STT-MRAM cell according to an embodiment of thepresent disclosure, the STT-MRAM cell including two fixed regions ofFIG. 5 disposed on either side, i.e., top and bottom, of a free region.

FIG. 8 is a cross-sectional, elevation, schematic illustration of a cellcore structure of an STT-MRAM cell according to an embodiment of thepresent disclosure, the STT-MRAM cell including the fixed region of FIG.5 and a narrow free region.

FIG. 9 is a cross-sectional, elevation, schematic illustration of a cellcore structure of an STT-MRAM cell according to an embodiment of thepresent disclosure, the STT-MRAM cell including the fixed region of FIG.5 and a free region of a structure according to an embodiment of thepresent disclosure.

FIG. 10 is a cross-sectional, elevation, schematic illustration of acell core structure of an STT-MRAM cell according to an embodiment ofthe present disclosure, the STT-MRAM cell including the fixed region ofFIG. 3 and the free region of FIG. 9.

FIG. 11 is a cross-sectional, elevation, schematic illustration of acell core structure of an STT-MRAM cell according to an embodiment ofthe present disclosure, the STT-MRAM cell including the fixed region ofFIG. 5, the free region of FIG. 9, and a reference region of a structureaccording to an embodiment of the present disclosure.

FIG. 12 is a simplified block diagram of a semiconductor devicestructure including memory cells of an embodiment of the presentdisclosure.

FIG. 13 is a simplified block diagram of a system implemented accordingto one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

Memory cells, semiconductor device structures including such memorycells, memory systems, and methods of forming such memory cells aredisclosed. The memory cells include a magnetic region exhibiting avertical magnetic orientation. The magnetic region includes one or moremagnetic materials and one or more coupler materials arranged such thatthe magnetic material alternates with the coupler material, forming whatis referred to herein as an “alternating structure,” in which an amountof magnetic material (i.e., a “magnetic sub-region”) is disposedadjacent to an amount of coupler material (i.e., a “coupler sub-region”)that is disposed adjacent to another amount of magnetic material (i.e.,another magnetic sub-region). Another amount of coupler material (i.e.,another coupler sub-region) may be disposed adjacent to the anotheramount of magnetic material (i.e., the another magnetic sub-region), andso on in sequence. Thus, the magnetic region of the memory cell includesan alternating structure of magnetic sub-regions and couplersub-regions.

The coupler material of the alternating structure is formulated toantiferromagnetically couple neighboring magnetic material. The couplermaterial may also effect a vertical magnetic orientation within theneighboring magnetic material. The magnetic sub-regions coupled by acoupler sub-region exhibit oppositely directed vertical magneticorientations. Therefore, the alternating structure of the magneticregion further includes magnetic sub-regions alternating in verticalmagnetic orientation.

Because the coupler material both provides antiferromagnetic couplingand effects the vertical magnetic orientations in the neighboringmagnetic material, a magnetic region with the alternating structureaccording to embodiments of the present disclosure may be thinner thanconventional magnetic regions that have one material providingantiferromagnetic coupling and another material to effect verticalmagnetic orientations. Therefore, the cell core of the memory cell maybe structured with a more compact structure than a cell core ofconventional memory cells.

Further, because the magnetic sub-regions within the magnetic region(e.g., the fixed region) may each be of thicknesses less than those ofmagnetic regions of a conventional MRAM memory cell's fixed region, amagnetic dipole field emitted by a magnetic sub-region may be smallerthan a magnetic dipole field emitted by a conventional magnetic region.The minimized magnetic dipole field reduces the interference of anemitted magnetic dipole field with the switching of the free region.

Moreover, because each magnetic sub-region within the magnetic region isclosely disposed to at least one neighboring magnetic sub-regionexhibiting an oppositely directed vertical magnetic orientation, amagnetic dipole field emitted by one magnetic sub-region may beeffectively substantially cancelled by another magnetic dipole fieldemitted closely nearby. This substantial cancellation reduces thelikelihood of a magnetic dipole field interfering with the switching ofthe free region.

As used herein, the term “substrate” means and includes a base materialor construction upon which components, such as those within memorycells, are formed. The substrate may be a semiconductor substrate, abase semiconductor material on a supporting structure, a metalelectrode, or a semiconductor substrate having one or more materials,structures, or regions formed thereon. The substrate may be aconventional silicon substrate or other bulk substrate including asemiconductive material. As used herein, the term “bulk substrate” meansand includes not only silicon wafers, but also silicon-on-insulator(“SOT”) substrates, such as silicon-on-sapphire (“SOS”) substrates orsilicon-on-glass (“SOG”) substrates, epitaxial layers of silicon on abase semiconductor foundation, or other semiconductor or optoelectronicmaterials, such as silicon-germanium (Si_(1-x)Ge_(x), where x is, forexample, a mole fraction between 0.2 and 0.8), germanium (Ge), galliumarsenide (GaAs), gallium nitride (GaN), or indium phosphide (InP), amongothers. Furthermore, when reference is made to a “substrate” in thefollowing description, previous process stages may have been utilized toform materials, regions, or junctions in the base semiconductorstructure or foundation.

As used herein, the term “STT-MRAM cell” means and includes a magneticcell structure that may include a magnetic tunnel junction (“MTJ”), if anon-magnetic region, disposed between the free region and the fixedregion, is electrically insulative (e.g., a dielectric). Alternatively,the magnetic cell structure of the STT-MRAM cell may include a spinvalve, if the non-magnetic region, disposed between the free region andthe fixed region, is electrically conductive.

As used herein, the term “cell core” means and includes a memory cellstructure comprising the free region and fixed region and through which,during operation of the memory cell, current flows to effect a parallelor anti-parallel magnetic orientation within the free region.

As used herein, the term “vertical” means and includes a direction thatis perpendicular to the width of the respective region. “Vertical” mayalso mean and include a direction that is perpendicular to a primarysurface of the substrate on which the STT-MRAM cell is located.

As used herein, the term “magnetic material” means and includes bothferromagnetic materials and ferrimagnetic materials.

As used herein, the term “coupler material” means and includes amaterial formulated to provide RKKY (Ruderman-Kittel-Kasuya-Yosida)interaction, also referred to herein as “anti-parallel coupling” or“antiferromagnetic coupling,” between neighboring regions of magneticmaterial and to effect or encourage a perpendicular anisotropy, i.e.,vertical magnetic orientation, within the neighboring regions ofmagnetic material. For example and without limitation, a couplermaterial according to embodiments of the present disclosure includesruthenium (Ru), rhodium (Rh), or combinations thereof.

As used herein, the term “neighboring,” when referring to a material,region, or sub-region, means and refers to a next, most proximatematerial, region, or sub-region of an identified composition. Materials,regions, or sub-regions of other compositions than the identifiedcomposition may be disposed between one material, region, or sub-regionand its neighboring material, region, or sub-region of the identifiedcomposition. For example, a magnetic sub-region “neighboring” aparticular coupler sub-region is the magnetic sub-region, e.g., of aplurality of magnetic sub-regions, that is next most proximate to theparticular coupler sub-region, which “neighboring” magnetic sub-regionmay be directly adjacent to the particular coupler sub-region. Asanother example, a magnetic sub-region “neighboring” a particularmagnetic sub-region is the magnetic sub-region, e.g., of a plurality ofmagnetic sub-regions, that is next most proximate to the particularmagnetic sub-region, which “neighboring” magnetic sub-region may bespaced from the particular magnetic sub-region by a material, region, orsub-region of a non-magnetic composition, e.g., a coupler material.

As used herein, the term “sub-region,” means and includes a regionincluded in another region. Thus, one region may include a plurality ofsub-regions.

As used herein, the term “fixed region” means and includes a regionwithin the STT-MRAM cell that includes magnetic material and that has afixed magnetic orientation during use and operation of the STT-MRAM cellin that a current effecting a change in the magnetization direction ofone magnetic region, e.g., the free region, of the cell core may noteffect a change in the magnetization direction of the fixed region.

As used herein, the term “free region” means and includes a regionwithin the STT-MRAM cell that includes magnetic material and that has aswitchable magnetic orientation during use and operation of the STT-MRAMcell. The magnetic orientation may be switched between a “parallel”direction, in which the magnetic orientation exhibited by the freeregion and the magnetic orientation exhibited by the fixed region aredirected in the same direction, and an “anti-parallel” direction, inwhich the magnetic orientation exhibited by the free region and themagnetic orientation exhibited by the fixed region are directed inmutually perpendicular, opposite directions.

As used herein, directionally relative terms, such as “upward,”“upwardly directed,” and the like, may be used for ease of descriptionto describe one magnetic orientation's or magnetic dipole field'sdirectional relationship to another magnetic orientation or magneticdipole field. Unless otherwise specified, the directionally relativeterms are intended to encompass different directions of the orientationsand fields in addition to the directions depicted in the figures. Forexample, if orientations are switched, magnetic orientations or magneticdipole fields described or illustrated as “upwardly directed” or“directed upward” would then be “downwardly directed” or “directeddownward” and magnetic orientations or magnetic dipole fields describedor illustrated as “downwardly directed” or “directed downward” wouldthen be “upwardly directed” or “directed upward.” Thus, the term“upward” encompasses a direction that is opposite that encompassed bythe term “downward.” Thus, for example, the term “upward” can encompassboth a direction from south to north and from north to south, and theterm “downward” can encompass both a direction from north to south andfrom south to north, respectively, depending on the context in which theterm is used, which will be evident to one of ordinary skill in the art.The magnetic orientations and magnetic dipole fields may be otherwiseoriented (rotated 90 degrees, inverted, etc.) and the directionallyrelative descriptors used herein interpreted accordingly.

As used herein, spatially relative terms, such as “beneath,” “below,”“lower,” “bottom,” “above,” “upper,” “top,” “front,” “rear,” “left,”“right,” and the like, may be used for ease of description to describeone element's or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. Unless otherwise specified,the spatially relative terms are intended to encompass differentorientations of the materials in addition to the orientation as depictedin the figures. For example, if materials in the figures are inverted,elements described as “below” or “beneath” or “under” or “on bottom of”other elements or features would then be oriented “above” or “on top of”the other elements or features. Thus, the term “below” can encompassboth an orientation of above and below, depending on the context inwhich the term is used, which will be evident to one of ordinary skillin the art. The materials may be otherwise oriented (rotated 90 degrees,inverted, etc.) and the spatially relative descriptors used hereininterpreted accordingly.

As used herein, reference to an element as being “on,” “over,” or“neighboring” another element means and includes the element beingdirectly on top of, adjacent to, underneath, or in direct contact withthe other element. It also includes the element being indirectly on topof, adjacent to, underneath, or near the other element, with otherelements present therebetween. In contrast, when an element is referredto as being “directly on” or “directly adjacent to” another element,there are no intervening elements present.

As used herein, the terms “comprises,” “comprising,” “includes,” and/or“including” specify the presence of stated features, regions, integers,stages, operations, elements, materials, components, and/or groups, butdo not preclude the presence or addition of one or more other features,regions, integers, stages, operations, elements, materials, components,and/or groups thereof.

As used herein, “and/or” includes any and all combinations of one ormore of the associated listed items.

As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise.

The illustrations presented herein are not meant to be actual views ofany particular material, component, region, sub-region, structure,device, or system, but are merely idealized representations that areemployed to describe embodiments of the present disclosure.

Embodiments are described herein with reference to the illustrations.Variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, embodiments described herein are not to be construed asbeing limited to the particular shapes or regions as illustrated butinclude deviations in shapes that result, for example, frommanufacturing. For example, a region illustrated or described asbox-shaped may have rough and/or nonlinear features. Moreover, sharpangles that are illustrated may, in practice, be rounded. Thus, theregions illustrated in the figures are schematic in nature and theirshapes are not intended to illustrate the precise shape of a region anddo not limit the scope of the present claims.

The following description provides specific details, such as materialtypes and processing conditions, in order to provide a thoroughdescription of embodiments of the disclosed devices and methods.However, a person of ordinary skill in the art will understand that theembodiments of the devices and methods may be practiced withoutemploying these specific details. Indeed, the embodiments of the devicesand methods may be practiced in conjunction with conventionalsemiconductor fabrication techniques employed in the industry.

The fabrication processes described herein do not form a completeprocess flow for processing semiconductor device structures. Theremainder of the process flow is known to those of ordinary skill in theart. Accordingly, only the methods and semiconductor device structuresnecessary to understand embodiments of the present devices and methodsare described herein.

Unless the context indicates otherwise, the materials described hereinmay be formed by any conventional technique including, but not limitedto, spin coating, blanket coating, chemical vapor deposition (“CVD”),plasma enhanced CVD, atomic layer deposition (“ALD”), plasma enhancedALD, or physical vapor deposition (“PVD”). Alternatively, the materialsmay be grown in situ. Depending on the specific material to be formed,the technique for depositing or growing the material may be selected bya person of ordinary skill in the art.

Reference will now be made to the drawings, wherein like numerals referto like components throughout. The drawings are not necessarily toscale.

A memory cell is disclosed. The memory cell includes a magnetic regionhaving magnetic material alternating with coupler material, e.g.,magnetic sub-regions alternating with coupler sub-regions. The couplermaterial antiferromagnetically couples neighboring magnetic sub-regionsand effects or encourages a vertical magnetic orientation exhibited bythe neighboring magnetic sub-regions. Magnetic sub-regions neighboringone another are spaced from one another by a coupler sub-region andexhibit oppositely directed vertical magnetic orientations. Thealternating magnetic sub-regions and coupler sub-regions may each be athickness configured to form the magnetic region (e.g., fixed region,free region) with a compact structure. Interference between magneticdipole fields emitted from the magnetic region on switching of a freeregion in the memory cell may be reduced or eliminated.

FIG. 4 illustrates an STT-MRAM system 400 that includes peripheraldevices 412 in operable communication with an STT-MRAM cell 414, aplurality of which may be fabricated to form an array of memory cells ina grid pattern including a number of rows and columns, or in variousother arrangements, depending on the system requirements and fabricationtechnology. The STT-MRAM cell 414 includes a cell core 402, an accesstransistor 403, a conductive material that may function as a data/senseline 404 (e.g., a bit line), a conductive material that may function asan access line 405 (e.g., a word line), and a conductive material thatmay function as a source line 406. The peripheral devices 412 of theSTT-MRAM system 400 may include read/write circuitry 407, a bit linereference 408, and a sense amplifier 409. The cell core 402 includes afree region and a fixed region with a non-magnetic region disposedtherebetween. One or both of the free region and the fixed region mayinclude an alternating structure of magnetic sub-regions and couplersub-regions. The coupler material of the coupler sub-regionsantiferromagnetically couples neighboring magnetic sub-regions andeffects a vertical magnetic orientation exhibited by the neighboringmagnetic sub-regions.

In use and operation, when an STT-MRAM cell 414 is selected to beprogrammed, a programming current is applied to the STT-MRAM cell 414,and the current is spin-polarized by the fixed region of the cell core402 and exerts a torque on the free region of the cell core 402, whichswitches the magnetization of the free region to “write to” or “program”the STT-MRAM cell 414. In a read operation of the STT-MRAM cell 414, acurrent is used to detect the resistance state of the cell core 402. Dueto the free region, the fixed region, or both regions having thealternating structure of the magnetic sub-regions and couplersub-regions, the critical switching current utilized to switch themagnetization of the free region from a parallel configuration to ananti-parallel configuration may be essentially the same as the criticalswitching current utilized to switch the magnetization of the freeregion from the anti-parallel configuration to the parallelconfiguration. Further, the alternating structure may further enable useof a cell core 402 with a smaller vertical dimension, thus providingimproved scalability and device density. The sequence of magneticsub-regions and coupler sub-regions may further enhance the stability ofthe magnetic region including such alternating structure.

To initiate programming of the STT-MRAM cell 414, the read/writecircuitry 407 may generate a write current to the data/sense line 404and the source line 406. The polarity of the voltage between thedata/sense line 404 and the source line 406 determines the switch inmagnetic orientation of the free region in the cell core 402. Once thefree region is magnetized according to the spin polarity of theprogramming current, the programmed state is written to the STT-MRAMcell 414.

To read the STT-MRAM cell 414, the read/write circuitry 407 generates aread voltage to the data/sense line 404 and the source line 406 throughthe cell core 402 and the access transistor 403. The programmed state ofthe STT-MRAM cell 414 relates to the resistance across the cell core402, which may be determined by the voltage difference between thedata/sense line 404 and the source line 406. In some embodiments, thevoltage difference may be compared to the bit line reference 408 andamplified by the sense amplifier 409.

With reference to FIG. 5, illustrated is a magnetic region, e.g., afixed region 530, of a memory cell according to an embodiment of thepresent disclosure. The fixed region 530 includes alternating magneticsub-regions 534 and coupler sub-regions 538. That is, the fixed region530 includes a plurality of magnetic sub-regions 534, each magneticsub-region 534 spaced from another magnetic sub-region 534 by one of thecoupler sub-regions 538. The coupler material of the coupler sub-regions538 antiferromagnetically couples neighboring magnetic sub-regions 534and effects therein oppositely directed vertical magnetic orientations531, 533. Therefore, one magnetic sub-region 534 exhibits the upwardvertical magnetic orientation 531 while a neighboring magneticsub-region 534, which is spaced from the one magnetic sub-region 534 byone coupler sub-region 538, exhibits the downward vertical magneticorientations 533. The number of alternating magnetic sub-regions 534 andcoupler sub-regions 538 may be tailored to achieve the appropriateoperation of the fixed region 530 or other magnetic region comprisingthe alternating structure while emitting little to no stray magneticdipole field.

The magnetic material of the magnetic sub-regions 534 may compriseferromagnetic materials or ferrimagnetic materials. For example, withoutlimitation, the magnetic material of the magnetic sub-regions 534 mayinclude Co, Fe, Ni or its alloys, NiFe, CoFe, CoNiFe, or doped alloysCoX, CoFeX, CoNiFeX (where X=B, Cu, Re, Ru, Rh, Hf, Pd, Pt, or C), orother half-metallic ferromagnetic material such as NiMnSb and PtMnSb,for example. In some embodiments, the magnetic material of the magneticsub-regions 534 may consist essentially of cobalt (Co), e.g., consistonly of cobalt (Co).

The coupler material of the coupler sub-regions 538 is formulated andpositioned to provide RKKY interaction between neighboring magneticsub-regions 534. The coupler material of the coupler sub-regions 538 isfurther formulated and positioned to effect or encourage the verticalmagnetic orientations 531, 533 exhibited by the neighboring magneticsub-regions 534. Thus, the coupler material of the coupler sub-regions538 is a dual-functioning material. Conventional magnetic regions ofMRAM cell structures, on the other hand, such as in the fixed region 330illustrated in FIG. 3, may include a region of coupler material, such asonly one layer of coupler material 338, to antiferromagnetically coupleregions, i.e., upper and lower regions, of the fixed region 330 whilealternating layers of conductive material 336, such as palladium orplatinum, are employed to effect the vertical magnetic orientations 331,333 within the layers of magnetic material 334. With continued referenceto FIG. 5, since fewer sub-regions are included in the fixed region 530according to embodiments of the present disclosure, or in other suchmagnetic regions utilizing the alternating structure of magneticsub-regions and coupler sub-regions, the structure of a magnetic region(e.g., the fixed region 530) may be more compact than that of aconventional magnetic region (e.g., fixed region 330 of FIG. 3). Forexample, a height of the fixed region 530 may be about one-half theheight of a conventional fixed region (e.g., the fixed region 330 ofFIG. 3). In some embodiments, the fixed region 530, or other magneticregion of an alternating structure according to the present disclosure,may be free of palladium, platinum, or both, because the functionaccomplished by such materials in a conventional magnetic region isaccomplished by the coupler material of the coupler sub-regions 538 ofthe magnetic region (e.g., fixed region 530) according to the presentdisclosure.

The coupler material of the coupler sub-regions 538 may be formed fromone or more materials formulated and positioned to antiferromagneticallycouple neighboring magnetic sub-regions 534. For example, withoutlimitation, the coupler material of the coupler sub-regions 538 may beformed from one or more of ruthenium (Ru) and rhodium (Rh).

Because the magnetic orientations 531, 533 alternate in verticaldirection, from one magnetic sub-region 534 to the neighboring magneticsub-region 534, a magnetic dipole field emitted by one of the magneticsub-regions 534 within the fixed region 530 may be substantially orwholly cancelled by an oppositely directed magnetic dipole field emittedby one or two neighboring magnetic sub-regions 534. Therefore, thelikelihood of a magnetic dipole field being generated from the fixedregion 530 and interfering with switching of a free region is minimized.

The thicknesses of the magnetic sub-regions 534 and coupler sub-regions538 may be tailored to achieve a desired outcome. In some embodiments,each sub-region 534, 538 is formed as a single monolayer of the magneticmaterial or coupler material, respectively. In other embodiments, eachsub-region 534, 538 includes about one monolayer to about fivemonolayers, e.g., about three monolayers, of the magnetic material orcoupler material, respectively. Each sub-region 534, 538 may define athickness (e.g., height) less than about one nanometer. For example, themagnetic sub-regions 534 may have a thickness (e.g., height) of lessthan about four angstroms (4 Å), e.g., a height of about 2 Å to about 3Å. In those or other embodiments, the coupler sub-regions 538 may have athickness (e.g., height) of less than about 6 Å, e.g., a height of about3 Å to about 5 Å, e.g., about 4 Å.

The fixed region 530, or other magnetic region utilizing the alternatingstructure of magnetic sub-regions 534 and coupler sub-regions 538, maybe formed by sequentially forming the coupler sub-regions 538 and themagnetic sub-regions 534, etc., i.e., forming a magnetic sub-region 534,then forming a coupler sub-region 538 on the magnetic sub-region 534,then forming another magnetic sub-region 534 on the coupler sub-region538, then forming another coupler sub-region 538 on the another magneticsub-region 534, etc. The lowest and uppermost sub-regions of the fixedregion 530, or other magnetic region with alternating structure, may bemagnetic sub-regions 534, as illustrated in FIG. 5.

The magnetic sub-regions 534 and the coupler sub-regions 538 may beformed by PVD, by sputtering, by another conventional material-formationprocess, or any combination thereof. The magnetic sub-regions 534 andthe coupler sub-regions 538 may be formed in the same fabrication tool.

The fabricated alternating structure of magnetic sub-regions 534 andcoupler sub-regions 538 (FIG. 5) may thereafter be patterned, i.e.,etched, along with other materials disposed above or below to form acell core structure 600, as illustrated in FIG. 6. Because the fixedregion 530 may be free of materials such as palladium and platinum,which are traditionally difficult to etch, patterning the fixed region530 to form the cell core structure 600 may be easier than patterning afixed region containing materials such as palladium and platinum, e.g.,the fixed region 330 of FIG. 3. Patterning may also be made easier dueto the compact structure of the fixed region 530, or other magneticregion of alternating structure, relative to the structure of aconventional fixed region (e.g., fixed region 330 of FIG. 3), or othermagnetic region without the alternating structure, respectively.

With continued reference to FIG. 6, the resulting cell core structure600 may include cell core regions below and above the fixed region 530.For example, the fixed region 530 may be formed over a lower conductivematerial 610 supported by the substrate 102. One or more lowerintermediary regions 620 may be disposed between the lower conductivematerial 610 and a lower surface of the fixed region 530. The lowerconductive material 610 may form part of a bottom electrode. The lowerintermediary region or regions 620 may include non-magnetic regions,transitional regions, diffusion barriers, buffers, compatibilityregions, other regions of a conventional STT-MRAM cell, or anycombination thereof.

Optionally, a transitional region 640, a reference region 650, or bothmay be formed above the fixed region 530. The transitional region 640,if included, may include a non-magnetic material, e.g., tantalum,titanium, nitrides thereof, or combinations thereof. The transitionalregion 640 may be formed to be of a thickness tailored such that theuppermost magnetic sub-region 534 (FIG. 5) of the fixed region 530 maymagnetically interact with the reference region 650, if included in thecell core structure 600. The transitional region 640, if included, maybe used to form the magnetic sub-regions 534 (FIG. 5) and the couplersub-regions 538 (FIG. 5) in a desired crystalline structure. Therefore,in some embodiments, the magnetic region of the alternating structure(e.g., fixed region 530) may include a superlattice structure of themagnetic sub-regions 534 (FIG. 5) and coupler sub-regions 538 (FIG. 5).

The reference region 650 may include magnetic material that may be ofthe same or different composition as the magnetic material of themagnetic sub-regions 534 (FIG. 5) of the fixed region 530. If present,the reference region 650 may exhibit a vertical magnetic orientationthat may influence a net vertical magnetic orientation of the fixedregion 530. For example, the reference region 650 may be magneticallypolarized and positioned to exhibit a downwardly directed verticalmagnetic orientation. In such a situation, the uppermost magneticsub-region 534 (FIG. 5) of the fixed region 530 may likewise exhibit adownwardly directed vertical magnetic orientation 533 (as illustrated inFIG. 5). In such embodiments, magnetic sub-regions 534 within the fixedregion 530 exhibiting an upwardly directed vertical magnetic orientation531 may be thicker than the magnetic sub-regions 534 exhibiting thedownwardly directed magnetic orientation 533 so as to achieve anessential cancellation of the downwardly directed magnetic orientations533 and the upwardly directed magnetic orientations 531 within the fixedregion 530 and the reference region 650.

With continued reference to FIG. 6, a non-magnetic region 660 may bedisposed between the fixed region 530 and a free region 670. Inembodiments in which the cell core structure 600 includes the referenceregion 650, the non-magnetic region 660 may be disposed between thereference region 650 and the free region 670. The non-magnetic region660 may comprise Al_(x)O_(y), MgO, AlN, SiN, CaO_(x), NiO_(x),Hf_(x)O_(y), Ta_(x)O_(y), Zr_(x)O_(y), NiMnO_(x), Mg_(x)F_(y), SiC,SiO₂, SiO_(x)N_(y), or any combination of the above materials. In someembodiments, the non-magnetic region 660 may comprise an electricallyinsulating material, and the non-magnetic region 660 may be configuredas an MTJ. In other embodiments, the non-magnetic region 660 maycomprise electrically conductive material, and the non-magnetic region660 may be configured as a spin valve.

The free region 670 includes magnetic material that may be of the sameor different composition as the magnetic material of the magneticsub-regions 534 (FIG. 5) within the fixed region 530. In someembodiments, the free region 670 may be a conventional free region,i.e., a magnetic region not including the alternating structure ofmagnetic sub-regions 534 (FIG. 5) and coupler sub-regions 538 (FIG. 5).

One or more upper intermediary regions 680 may be formed over the freeregion 670, and an upper conductive region 690 may be formed as theuppermost region of the cell core structure 600. The upper intermediaryregions 680, if included, may be any one or more of the regionsdiscussed above with regard to the lower intermediary region or regions620. The upper conductive region 690 may form a part of a top electrode,such that the upper conductive region 690 may function as the data/senseline 404 (FIG. 4). The cell core structure 600 may therefore beimplemented in the STT-MRAM cell 414 of FIG. 4.

Though FIG. 6 depicts the free region 670 as being disposed above thefixed region 530, in other embodiments, the free region 670 may bedisposed below the fixed region 530. Further, one of ordinary skill inthe art will recognize that the magnetic orientations (e.g., magneticorientations 531, 533 of FIG. 5) could be oppositely illustrated withoutaltering the function of the respective magnetic sub-regions (e.g.,magnetic sub-regions 534 of FIG. 5).

The cell core structure 600 of FIG. 6 may achieve a substantiallysymmetrically switchable free region 670 because the compact,alternating structure of the fixed region 530 is such that magneticdipole fields emitted from the fixed region 530 are minimized (e.g., dueto the thin dimension of the magnetic sub-regions 534 (FIG. 5)) and aresubstantially cancelled (e.g., due to the alternating pattern ofoppositely oriented magnetic sub-regions 534 (FIG. 5)). Further, becausethe materials of a plurality of cell core structures 600 could be formedand then patterned simultaneously, the structure of the fixed region 530may accommodate forming a number of cell core structures 600 withsubstantial uniformity among the cell core structures 600 so formed.

Magnetic regions of the alternating structure, i.e., alternatingmagnetic sub-regions 534 and coupler sub-regions 538, such as the fixedregion 530 illustrated in FIGS. 5 and 6, may be utilized elsewhere in acell core structure of a magnetic memory cell. Such magnetic regions ofalternating structures may be configured to function as additional fixedregions, as free regions, as reference regions, or any combinationthereof. The number of sub-regions, the materials, and the dimensionsutilized in the alternating structure may be tailored to achieve thedesired functionality of the fixed region, free region, referenceregion, or combinations thereof, respectively. For example, the numberof sub-regions included in a free region may be a number selected toaccommodate switching of the magnetic orientation of the free regionduring operation of the MRAM cell, while the number of sub-regionsincluded in a fixed region may be a number selected to avoid switchingof the magnetic orientation during operation.

Further, though the alternating structure, e.g., the structure of thefixed region 530 (FIG. 5), as disclosed and described herein, minimizesthe negative interference between a stray magnetic dipole field from thefixed region 530 and the free region (e.g., free region 670 of FIG. 6),the structure of the cell core may be further configured to minimizesuch interference.

For example, with reference to FIG. 7, according to another embodimentof the present disclosure, a cell core structure 700 may include morethan one fixed region 530, e.g., two fixed regions 530, each having analternating structure as illustrated and discussed above with regard toFIG. 5. The fixed regions 530 may be disposed essentially symmetricallyabove and below the free region 670. As such, the cell core structure700 may be configured so that a magnetic dipole field emitted toward thefree region 670 by one of the fixed regions 530 may be cancelled by amagnetic dipole field emitted toward the free region 670, from the otherdirection, by another of the fixed regions 530. Therefore, not only doesthe cell core structure 700 minimize the magnetic dipole fieldinterference by utilizing the alternating structure of magneticsub-regions 534 (FIG. 5) and coupler sub-regions 538 (FIG. 5), it alsosymmetrically disposes fixed regions 530 relative to the free region 670to further cancel stray magnetic dipole fields.

As another example, with reference to FIG. 8, in another cell corestructure 800 according to an embodiment of the present disclosure, afree region 870 may be formed to have a smaller lateral dimension (e.g.,width) than a lateral dimension (e.g., width) of the fixed region 530.The cell core structure 800 may therefore be configured to inhibitinterference between a magnetic dipole field emitted by the fixed region530, which may be emitted most strongly near sidewalls of the fixedregion 530, and the free region 870, which, as illustrated, may notvertically overlap the sidewalls of the fixed region 530 from which themagnetic dipole field is most strongly emitted. Therefore, thealternating structure of the fixed region 530 and the narrower freeregion 870 each minimize magnetic dipole field interference of the freeregion 870 switching.

As still another example, with reference to FIG. 9, a cell corestructure 900 may include not only the fixed region 530 having thealternating structure, but also a free region 970 with an alternatingstructure. The number of alternating magnetic sub-regions 534 (FIG. 5)and coupler sub-regions 538 (FIG. 5) may be tailored to ensureswitchability of the magnetic orientation of the free region 970 duringoperation. In some such embodiments, the free region 970 may includefewer alternating sub-regions than the fixed region 530. Because of thealternating structure, the effects of stray magnetic dipole fields maybe further minimized.

In other embodiments, such as that illustrated in FIG. 10, a cell corestructure 1000 may utilize the alternating structure in the free region970 but not in other magnetic regions, such as in the fixed region.Accordingly, the free region 970 of the present disclosure may beutilized in conjunction with a conventional fixed region, e.g., thefixed region 330 of FIG. 3. The free region 970 of the alternatingstructure may nonetheless experience less switching interference fromstray magnetic dipole fields (e.g., a magnetic dipole field emitted bythe fixed region 330) than a free region of a conventional cell corestructure (e.g., free region 670 of FIG. 7).

In still other embodiments, each of the magnetic regions of a cell corestructure 1100 may include the alternating structure, as illustrated inFIG. 11. Accordingly, each of the fixed region 530, the free region 970,and a reference region 1150 may include the alternating structure ofmagnetic sub-regions 534 (FIG. 5) and coupler sub-regions 538 (FIG. 5).Again, the number of alternating sub-regions, the materials thereof, thedimensions (e.g., thicknesses, widths) thereof, and the dispositionsthereof relative to other magnetic regions may be tailored to ensureeffective operation of the cell core structure 1100. For example, thereference region 1150 may include fewer alternating sub-regions than thefree region 970, which may include fewer alternating sub-regions thanthe fixed region 530.

Accordingly, disclosed is a memory cell comprising a magnetic region.The magnetic region comprises an alternating structure of magneticmaterial and coupler material. The magnetic region exhibits a verticalmagnetic orientation.

Also disclosed is a method of forming a memory cell, comprising forminga magnetic region. Forming a magnetic region comprises forming amagnetic sub-region exhibiting a vertical magnetic orientation. Acoupler sub-region is formed on the magnetic sub-region. Anothermagnetic sub-region is formed on the coupler sub-region. The anothermagnetic sub-region exhibits another vertical magnetic orientationoppositely directed to the vertical magnetic orientation exhibited bythe magnetic sub-region. Another coupler sub-region is formed on theanother magnetic sub-region.

Moreover, disclosed is a memory cell comprising at least two magneticregions. At least one of the at least two magnetic regions comprisescoupler sub-regions. Each of the coupler sub-regions is separated fromanother of the coupler sub-regions by a magnetic sub-region exhibiting avertical magnetic orientation.

Further, disclosed is a memory cell comprising a magnetic regioncomprising a plurality of magnetic sub-regions. At least one magneticsub-region of the plurality exhibits a vertical magnetic orientationwith opposing vertical magnetic orientations exhibited by a pair ofneighboring magnetic sub-regions of the plurality.

Also disclosed is a semiconductor device structure including at leastone STT-MRAM cell, e.g., an array of STT-MRAM cells. With reference toFIG. 12, illustrated is a simplified block diagram of a semiconductordevice structure 1200 implemented according to one or more embodimentsdescribed herein. The semiconductor device structure 1200 includes amemory array 1202 and a control logic component 1204. The memory array1202 may include a plurality of the STT-MRAM cells 414 (FIG. 4)including any of the cell core structures 600 (FIG. 6), 700 (FIG. 7),800 (FIG. 8), 900 (FIG. 9), 1000 (FIG. 10), 1100 (FIG. 11) discussedabove, which cell core structures 600, 700, 800, 900, 1000, 1100 mayhave been formed according to a method described above. The controllogic component 1204 may be configured to operatively interact with thememory array 1202 so as to read from or write to any or all memory cells(e.g., STT-MRAM cell 414) within the memory array 1202.

Accordingly, disclosed is a semiconductor device structure comprising aspin torque transfer magnetic random-access memory (STT-MRAM) array. Thearray comprises a plurality of STT-MRAM cells. Each STT-MRAM cell of theplurality comprises a cell core comprising a magnetic region exhibitinga vertical magnetic orientation. The magnetic region comprises aplurality of spaced sub-regions of a coupler material.

Also disclosed is a system including a memory array, e.g., memory array1202. With reference to FIG. 13, depicted is a processor-based system1300. The processor-based system 1300 may include various electronicdevices manufactured in accordance with embodiments of the presentdisclosure. The processor-based system 1300 may be any of a variety oftypes such as a computer, pager, cellular phone, personal organizer,control circuit, or other electronic device. The processor-based system1300 may include one or more processors 1302, such as a microprocessor,to control the processing of system functions and requests in theprocessor-based system 1300. The processor 1302 and other subcomponentsof the processor-based system 1300 may include magnetic memory devicesmanufactured in accordance with embodiments of the present disclosure.

The processor-based system 1300 may include a power supply 1304. Forexample, if the processor-based system 1300 is a portable system, thepower supply 1304 may include one or more of a fuel cell, a powerscavenging device, permanent batteries, replaceable batteries, andrechargeable batteries. The power supply 1304 may also include an ACadapter; therefore, the processor-based system 1300 may be plugged intoa wall outlet, for example. The power supply 1304 may also include a DCadapter such that the processor-based system 1300 may be plugged into avehicle cigarette lighter, for example.

Various other devices may be coupled to the processor 1302 depending onthe functions that the processor-based system 1300 performs. Forexample, a user interface 1306 may be coupled to the processor 1302. Theuser interface 1306 may include input devices such as buttons, switches,a keyboard, a light pen, a mouse, a digitizer and stylus, a touchscreen, a voice recognition system, a microphone, or a combinationthereof. A display 1308 may also be coupled to the processor 1302. Thedisplay 1308 may include an LCD display, an SED display, a CRT display,a DLP display, a plasma display, an OLED display, an LED display, athree-dimensional projection, an audio display, or a combinationthereof. Furthermore, an RF sub-system/baseband processor 1310 may alsobe coupled to the processor 1302. The RF sub-system/baseband processor1310 may include an antenna that is coupled to an RF receiver and to anRF transmitter (not shown). A communication port 1312, or more than onecommunication port 1312, may also be coupled to the processor 1302. Thecommunication port 1312 may be adapted to be coupled to one or moreperipheral devices 1314, such as a modem, a printer, a computer, ascanner, or a camera, or to a network, such as a local area network,remote area network, intranet, or the Internet, for example.

The processor 1302 may control the processor-based system 1300 byimplementing software programs stored in the memory. The softwareprograms may include an operating system, database software, draftingsoftware, word-processing software, media-editing software, ormedia-playing software, for example. The memory is operably coupled tothe processor 1302 to store and facilitate execution of variousprograms. For example, the processor 1302 may be coupled to systemmemory 1316, which may include one or more of spin torque transfermagnetic random-access memory (STT-MRAM), magnetic random-access memory(MRAM), dynamic random-access memory (DRAM), static random-access memory(SRAM), racetrack memory, and other known memory types. The systemmemory 1316 may include volatile memory, non-volatile memory, or acombination thereof. The system memory 1316 is typically large so thatit can store dynamically loaded applications and data. In someembodiments, the system memory 1316 may include semiconductor devicestructures, such as the semiconductor device structure 1200 of FIG. 12,memory cells including any of cell core structures 600 (FIG. 6), 700(FIG. 7), 800 (FIG. 8), 900 (FIG. 9), 1000 (FIG. 10), 1100 (FIG. 11), ora combination thereof.

The processor 1302 may also be coupled to non-volatile memory 1318,which is not to suggest that system memory 1316 is necessarily volatile.The non-volatile memory 1318 may include one or more of STT-MRAM, MRAM,read-only memory (ROM) such as an EPROM, resistive read-only memory(RROM), and Flash memory to be used in conjunction with the systemmemory 1316. The size of the non-volatile memory 1318 is typicallyselected to be just large enough to store any necessary operatingsystem, application programs, and fixed data. Additionally, thenon-volatile memory 1318 may include a high capacity memory such as diskdrive memory, such as a hybrid-drive including resistive memory or othertypes of non-volatile solid-state memory, for example. The non-volatilememory 1318 may include semiconductor device structures, such as thesemiconductor device structure 1200 of FIG. 12, memory cells includingany of cell core structures 600 (FIG. 6), 700 (FIG. 7), 800 (FIG. 8),900 (FIG. 9), 1000 (FIG. 10), 1100 (FIG. 11), or a combination thereof.

Accordingly, disclosed is a spin torque transfer magnetic random-accessmemory (STT-MRAM) system, comprising at least one magnetic memory cellcomprising a magnetic region comprising a plurality of sub-regions ofmagnetic material. A sub-region of the plurality exhibits a verticalmagnetic orientation oppositely directed to another vertical magneticorientation exhibited by another sub-region of the plurality. TheSTT-MRAM system also comprises at least one peripheral device inoperable communication with the at least one magnetic memory cell.

While the present disclosure is susceptible to various modifications andalternative forms in implementation thereof, specific embodiments havebeen shown by way of example in the drawings and have been described indetail herein. However, the present disclosure is not intended to belimited to the particular forms disclosed. Rather, the presentdisclosure encompasses all modifications, combinations, equivalents,variations, and alternatives falling within the scope of the presentdisclosure as defined by the following appended claims and their legalequivalents.

What is claimed is:
 1. An apparatus, comprising: a fixed regionexhibiting a fixed vertical magnetic orientation; and a free regionexhibiting a switchable vertical magnetic orientation, the free regioncomprising an alternating structure of magnetic sub-regions and couplersub-regions, at least one of the magnetic sub-regions having anoppositely directed magnetic orientation as a magnetic orientation oftwo of the nearest magnetic sub-regions.
 2. The apparatus of claim 1,wherein the magnetic sub-regions comprise cobalt, nickel, iron, oralloys thereof.
 3. The apparatus of claim 1, wherein the couplersub-regions comprise one or both of ruthenium and rhodium.
 4. Theapparatus of claim 1, wherein a magnetic dipole field emitted by amagnetic sub-region of the magnetic sub-regions is configured to besubstantially canceled by an oppositely directed magnetic dipole filedemitted from one or two neighboring magnetic sub-regions of the one ofthe magnetic sub-regions.
 5. The apparatus of claim 1, wherein each ofthe magnetic sub-regions and the coupler sub-regions individuallycomprise a monolayer.
 6. The apparatus of claim 1, wherein each of themagnetic sub-regions and the coupler sub-regions individually comprisefrom about one monolayer to about five monolayers.
 7. The apparatus ofclaim 1, wherein the fixed region comprises another alternatingstructure of magnetic sub-regions and coupler sub-regions.
 8. Theapparatus of claim 7, wherein the free region comprises feweralternating magnetic sub-regions and coupler sub-regions than the fixedregion.
 9. The apparatus of claim 1, wherein the free region comprisesone more coupler sub-region than a number of magnetic sub-regions.
 10. Acell core structure, comprising: a fixed region exhibiting a fixedvertical magnetic orientation; a transitional region adjacent to thefixed region; and a free region exhibiting a switchable verticalmagnetic orientation adjacent to the transitional region, one or both ofthe fixed region and the free region comprising an alternating structureof magnetic sub-regions and coupler sub-regions, more than one of themagnetic sub-regions located between two other magnetic sub-regions andhaving an oppositely directed magnetic orientation relative to amagnetic orientation of the two other magnetic sub-regions.
 11. The cellcore structure of claim 10, wherein the transitional region comprises anon-magnetic material.
 12. The cell core structure of claim 10, whereinthe transitional region comprises tantalum, titanium, nitrides thereof,or combinations thereof.
 13. The cell core structure of claim 10,further comprising a non-magnetic material adjacent to the transitionalregion and between the free region and the fixed region.
 14. The cellcore structure of claim 10, wherein an uppermost sub-region of thealternating structure comprises a coupler sub-region and a lowermostsub-region of the alternating structure comprises a coupler sub-region.15. The cell core structure of claim 10, wherein the free region isconfigured to emit a stronger magnetic dipole field near sidewallsthereof.
 16. A system, comprising: a processor; and a magnetic structurecomprising a magnetic cell core coupled to the processor, the magneticcell core comprising: a fixed region comprising a first alternatingstructure of magnetic sub-regions and coupler sub-regions, each magneticsub-region spaced from another magnetic sub-region by one of the couplersub-regions and having an oppositely directed magnetic orientation asneighboring magnetic sub-regions; a non-magnetic region adjacent to thefixed region; and a free region adjacent to the non-magnetic region, thefree region comprising a second alternating structure of magneticsub-regions and coupler sub-regions, each magnetic sub-region spacedfrom another magnetic sub-region by one of the coupler sub-regions andhaving an oppositely directed magnetic orientation as neighboringmagnetic sub-regions.
 17. The system of claim 16, wherein each couplersub-region of the fixed region effects anti-parallel coupling in atleast one adjacent magnetic sub-structure of the fixed region.
 18. Thesystem of claim 16, further comprising a reference region comprising amagnetic material between the fixed region and the free region.
 19. Thesystem of claim 18, wherein the reference region comprises a thirdalternating structure of magnetic sub-regions and coupler sub-regions.20. The system of claim 19, wherein the reference region comprises fewermagnetic sub-regions and coupler sub-regions than the free region.